Patent FR-2909291-A1 (FR)
Title: Washing hollow fiber membranes and inner or outer skin of filtration installation comprises introducing water to be treated by feeding conduit, collecting treated water by collector, and evacuating water by waste collector
Inventor: BOURDIOL DANIEL
IPC: B01D29/66
Filed: 2006-12-01
Abstract: The method for washing hollow fiber membranes and inner or outer skin of a filtration installation comprises introducing a water to be treated by a feeding conduit (1) on which modules are connected in parallel or in groups, collecting the treated water by a collector, and evacuating the water by a waste collector parallelly connected on sweeping outlet of the modules. The installation comprises three modules or groups of modules in which each module comprises parallelly branched hollow fibers (3). Ends of the fibers are closed during filtration. The method for washing hollow fiber membranes and inner or outer skin of a filtration installation comprises introducing a water to be treated by a feeding conduit (1) on which modules are connected in parallel or in groups, collecting the treated water by a collector, and evacuating the water by a waste collector parallelly connected on sweeping outlet of the modules. The installation comprises three modules or groups of modules in which each module comprises parallelly branched hollow fibers (3). Ends of the fibers are closed during filtration. The collector comprises a valve for production of all downstream modules. The washing is obtained by sweeping or flushing on the surface of concentrated fibers when the collector of treated liquid is closed. Fixing of an upstream valve takes place between each module or group of modules and feeding conduit, while a downstream valve is fixed between each module or group of modules and the waste water collector. The sweeping of a module or group of modules is carried out by closing the downstream valves of other modules and the valve for production of treated water and by keeping the downstream valve and the upstream valve of a module to be sweeped open, so that the complete flow crosses the single module or group of modules. During sweeping, the water is introduced to an axial end of fibers of module and evacuated to the other axial end through the open downstream valve towards the waste collector. The fibers are laid in closed casing and sweeping takes place on the outer surface of fibers by introducing water at one end of the casing and recovery of water at the other end of the casing. A counter pressure is exerted around the hollow fibers or inner side of hollow fibers to prevent a filtration occurs in areas of fiber placed in greater pressure of the concentrate side than permeate side, and to create a mini-backwash along the entire length of fibers. Rising of the sweeping speed is obtained without the raise of nominal flow of the installation, by carrying out that sweeping in the filtration modules one after the others. The groups of modules are constituted of several modules hydraulically connected in parallel or in series, in a same casing or in the different casings. The sweeping with counter pressure corresponding to a pressure in the treated water greater than the pressure in the water to be treated is carried out along the entire length of the membranes. The counter pressure is obtained by a tank under pressure and through a liquid stock and an extra pump. The counter pressure is based on losses by the upstream valve of the module by flushing and the upstream valve of other modules is open. Conducting a series of flush allowing a flush of all modules for a balance between different modules, begins with a module different for each series. The sweeping of the membrane surfaces is carried out by a diphasic gas mixture such as air and water. An independent claim is included for a device.